Anyway, there are topics, which are not handled in the documentation. On the page about Special topics concerning emacs customization you'll find some of them.

Links to the Emacs documentation nodes which handle customization

and

Customization

• Minor Modes
• Variables
  • Examining and Setting Variables
  • Easy Customization Interface
    • Customization Groups
    • Changing an Option
    • Customizing Faces
    • Customizing Specific Items
  • Hooks
  • Local Variables
  • Local Variables in Files
• Keyboard Macros
  • Basic Use
  • Naming and Saving Keyboard Macros
  • Executing Macros with Variations
• Customizing Key Bindings
  • Keymaps
  • Prefix Keymaps
  • Local Keymaps
  • Minibuffer Keymaps
  • Changing Key Bindings Interactively
  • Rebinding Keys in Your Init File
  • Rebinding Function Keys
  • Named ASCII Control Characters
  • Non-ASCII Characters on the Keyboard
  • Rebinding Mouse Buttons
  • Disabling Commands
• Keyboard Translations
• The Syntax Table
• The Init File, `~/.emacs'
  • Init File Syntax
  • Init File Examples
  • Terminal-specific Initialization
  • How Emacs Finds Your Init File